WHY THIS RECIPE WORKS This savory, flaky, rustic tart starring butternut squash and baby spinach is bound to be a favorite on any fall or winter table. In developing this recipe, we were looking for a filling that was robust and flavorful and a crust that was extra-sturdy while still being tender, moist, and flaky. To achieve that goal with a dough using wholewheat flour, we decided to take a hands-off approach to mixing and let the flour absorb the water on its own. We thought this might allow the water to migrate to drier parts and produce pastry that was workable—but not overworked. So we gave it a shot, just barely mixing the dry and wet ingredients and then chilling the dough. After an hour, most of the dry flour had disappeared; even better, the dough was remarkably supple. To get the long, striated layers of puff pastry we were after, we dumped the rested shaggy mass onto the counter, rolled it into a rectangle, and folded it into thirds, like a business letter. We repeated the process just twice more. The result? A wonderfully flaky crust that was less apt to shatter when cut. Working with a sturdy crust, however, didn’t mean that we could throw in the vegetables—spinach and butternut squash—raw: They’d still leach far too much moisture and render the crust soggy. Fortunately, parcooking the spinach and squash separately in the microwave took only a few minutes. To introduce rich, complex flavor and not too much moisture, we added sautéed onion, a dollop of crème fraîche, Gruyère, and a splash of sherry vinegar to the vegetables just before baking. An equal amount of rye flour can be substituted for the wholewheat flour. Cutting a few small holes in the dough prevents it from lifting off the pan as it bakes. A pizza stone helps to crisp the crust but is not essential.

Serves 4 to 6

TOTAL TIME: 1 hour 45 minutes (plus 1 hour 30 minutes chilling time)

INGREDIENTS

• FOR DOUGH:
• 1¼ cups (6¼ ounces) all-purpose flour
• ½ cup (2¾ ounces) whole-wheat flour
• 1 tablespoon sugar
• ¾ teaspoon salt
• 10 tablespoons unsalted butter, cut into ½-inch pieces and chilled
• 7 tablespoons ice water
• 1 teaspoon distilled white vinegar

• FOR FILLING:
• 6 ounces (6 cups) baby spinach
• 1¼ pounds butternut squash, peeled and cut into ½-inch pieces (3½ cups)
• 5 teaspoons extra-virgin olive oil
• 1 red onion, sliced thin
• ½ teaspoon minced fresh oregano
• 3 ounces Gruyère cheese, shredded (¾ cup)
• 2 tablespoons crème fraîche
• 1 teaspoon sherry vinegar
• Salt and pepper
• 1 large egg, lightly beaten
• 2 tablespoons minced fresh parsley

INSTRUCTIONS

• FOR DOUGH:

1. Process all-purpose flour, whole-wheat flour, sugar, and salt in food processor until combined.
2. Scatter chilled butter over top and pulse until butter is pea-sized, about 10 pulses; transfer to medium bowl.
3. Sprinkle ice water and vinegar over flour mixture. Using rubber spatula, fold mixture until loose, shaggy mass forms with some dry flour remaining (do not overwork).
4. Transfer to center of large sheet of plastic wrap, press gently into rough 4-inch square, and wrap tightly. Refrigerate for 45 minutes.
5. Transfer dough to lightly floured counter and roll into 11 by 8-inch rectangle with short side parallel to edge of counter.
6. Using bench scraper, fold bottom third of dough away from you, then fold upper third toward you like business letter into 8 by 4-inch rectangle.
7. Turn dough 90 degrees counterclockwise. Repeat rolling dough into 11 by 8-inch rectangle and folding into thirds.
8. Turn dough 90 degrees counterclockwise and repeat rolling and folding into thirds.
9. After last set of folds, fold dough in half to create 4-inch square. Press top of dough gently to seal. Wrap with plastic and refrigerate for at least 45 minutes or up to 2 days.

• FOR FILLING:

1. Microwave spinach and ¼ cup water in large bowl, covered, until spinach is shrunk by half, 3 to 4 minutes.
2. Remove bowl from microwave and set aside, covered, for 1 minute.
3. Transfer spinach to colander to drain. Using back of rubber spatula, gently press spinach to release excess liquid.
4. Transfer spinach to cutting board and chop coarse. Return spinach to colander and press again with rubber spatula; set aside.
5. Add squash to now-empty bowl and microwave, covered, until just tender, about 8 minutes; set aside.
6. Meanwhile, heat 1 tablespoon oil in 12-inch skillet over medium heat until shimmering.
7. Add onion and oregano, cover, and cook, stirring frequently, until onion is tender and beginning to brown, 5 to 7 minutes.
8. Off heat, add onion mixture to bowl with squash along with spinach, Gruyère, crème fraîche, and vinegar and stir gently to combine.
9. Season with salt and pepper to taste and set aside.

• FOR ASSEMBLY:

1. Adjust oven rack to lower-middle position, place pizza stone on rack, and heat oven to 400 degrees.
2. Line rimmed baking sheet with parchment paper.
3. Remove dough from refrigerator and let stand at room temperature for 15 to 20 minutes.
4. Roll dough into 14-inch circle about ⅛ inch thick on well-floured counter. (Trim edges as needed to form rough circle).
5. Transfer dough to prepared sheet. Using straw or tip of paring knife, cut five ¼-inch circles in dough (one at center and four evenly spaced halfway from center to edge of dough).
6. Brush top of dough with 1 teaspoon oil.
7. Spread filling evenly over dough, leaving 2-inch border around edge. Drizzle remaining 1 teaspoon oil over filling.
8. Grasp 1 edge of dough and fold outer 2 inches over filling. Repeat around circumference of tart, overlapping dough every 2 to 3 inches; gently pinch pleated dough to secure but do not press dough into filling.
9. Brush dough with egg wash.
10. Reduce oven temperature to 375 degrees. Set sheet on stone and bake until crust is deep golden brown and filling is beginning to brown, 35 to 45 minutes. Let tart cool on sheet on wire rack for 10 minutes. Using offset or wide metal spatula, loosen tart from parchment and carefully slide tart onto cutting board. Sprinkle parsley over filling and cut tart into wedges.
11. Serve.